Recent Advances: Cardiology - I: Treatment of myocardial infarction, unstable angina, and angina pectoris

Abstract

Myocardial infarction and thrombolysis Early thrombolysis Two recent large trials, EMIP and the MITI project, have compared thrombolysis started before admission to hospital with that started in hospital, which adds to the findings of GREAT (table I).*RF 1-3* The results of EMIP and the MITI project were much less encouraging than those of GREAT, showing only a marginal benefit during short term follow up for prehospital treatment over hospital treatment (table I). This difference between GREAT and the two recent trials probably reflects the much shorter delay in starting thrombolysis in hospital in EMIP and the MITI project. This, in part, reflected the effect of the trials on “usual practice.” In EMIP the median time from arrival in hospital to injection was only 15 minutes compared with over 80 minutes in recent British and American surveys.4 In support of this, patients in the MITI project who were treated within 70 minutes of the onset of symptoms had a mortality in hospital of only 1.2% compared with 8.7% in those who were not treated within 70 minutes (P=0.04). The clear message of these studies is the earlier treatment is given the better: when matters more than where. View this table: In this window In a new window TABLE I Trials of prehospital thrombolysis Initiating thrombolysis just 30-60 minutes earlier, the sort of time saving that can be achieved by regular audit and the introduction of fast track systems, will typically save about 15 extra lives for each 1000 patients treated (see discussion of GUSTO study below).4 An even greater benefit may be obtained if treatment is given within the first hour after the onset of symptoms (fig 1).5 View larger version: In this window In a new window FIG 1 Time dependent benefits of thrombolysis. Graph shows absolute reduction in mortality at 35 days v delay from onset of symptoms to randomisation among 45 000 patients with ST elevation or bundle branch block. Vertical lines show standard deviation5 A British Heart Foundation working group has recommended that the time between calling the emergency services and receiving thrombolysis should ideally be less than 60 minutes and certainly no more than 90 minutes.4 Initiating thrombolysis before arrival in hospital may need to be considered if it is the only way to achieve the 90 minute target - for example, in rural areas.